The biogenesis of the photosynthetic thylakoid membranes inside plant chloroplasts requires enzymes at the plastid envelope and the endoplasmic reticulum (ER). Extensive lipid trafficking is required for thylakoid lipid biosynthesis. Trigalactosyldiacylglycerol (TGD) proteins are believed to be permease components of a bacterial-type ATP-Binding Cassette (ABC) transporter located in the chloroplast inner envelope membrane.
Trigalactosyldiacylglycerol proteins were suggested to have a phosphatidic acid-binding protein with a predicted mycobacterial-like cell entry domain such that they may be tethered to the inner chloroplast envelope membrane facing the outer envelope membrane. However, these specific phosphatidic acid binding sites had not been identified, purified and/or isolated.
This lack of knowledge has hampered the development of specific diagnostic and detection methods designed to detect and quantify phosphatidic acid in plants. What is needed in the art is a reliable, quantitatively sensitive, and routine laboratory assay to detect for the purposes of botanical diagnostics and as a laboratory research tool.